1. Field of the Invention
The present invention relates to a laser recording apparatus such as a laser beam printer or a digital photocopier capable of opening vertically.
2. Description of the Related Art
FIG. 13 shows a digital photocopier which is a known laser recording apparatus. This digital photocopier is capable of being opened vertically in a clamshell-like manner, and is arranged so as to control a laser beam according to an image signal optically read from an original document, and to scan the controlled laser beam so as to form an image on a photosensitive member 101. The digital photocopier also comprises a scanner unit 102, laser printer unit 103, paper feeding unit 104, and sorter 105.
The scanner unit 102 comprises an original document table 106, reversible automatic document feeder (RADF) 107, and a scannerunit 108. The RADF 107 is provided for setting a plurality of original documents thereupon, of which one document at a time is fed to the scanner unit 108, either one or both sides thereof being read by the scanner unit 108 according to selection by the operator. The scanner unit 108 has a lamp reflector assembly 109 provided with a lamp for illuminating the original document, and a mirror 111 and lens 112 for guiding light reflected from the document to a photoelectric converting device (CCD) 110.
In the case that the RADF 107 is not employed, the scanner unit 102 is arranged so as to move following the bottom surface of the original document table 106 and thus read the original image, and in the case where the RADF 107 is employed, the scanner unit 108 is set in a stationary position below the RADF 107 over which the original document is conveyed, thus facilitating reading of the original document.
The image data obtained by reading the original document with the scanner unit 108 is sent to an image processing unit within a control unit, comprised of a micro-computer and subjected to various processes, and then is temporarily stored in a data recording portion of the image processing unit. The image data within this data recording portion is handed to the laser printer unit 103 according to output instructions, and the image is formed on recording paper.
The laser printer unit 103 comprises a manual-feed original tray 113, laser recording unit 114, and an electrophotography processing unit 115 for forming images. As shown in FIG. 14, the laser recording unit 114 has laser beam irradiating means 116 for irradiating a laser beam modulated by an image signal, laser scanning means 117 for laser scanning the laser beam irradiated from the laser beam irradiating means 116, laser beam detecting means 118 for detecting a portion of the laser beam and manage recording of the image on the photosensitive member 101, and optical means 119 for guiding the laser beam scanned by the laser scanning means 117 onto the photosensitive member 101 thus forming an image thereon. These form one unit, and are contained within a box-shaped unit proper 120.
The laser beam irradiating means 116 comprises a slit semiconductor laser (not shown) for emitting a laser beam according to image data from the data recording unit, a laser oscillation substrate 121, a collimator lens 122 for converging the laser beam in a parallel manner, and a cylindrical lens 124 for correcting planar inclination of the polygon mirror 123. The laser scanning means 117 comprises a polygon mirror 123 which performs isometric speed deviation of the laser beam, and a polygon motor 125 which supports the polygon mirror 123. The optical means 119 comprises f-.theta. lenses 126a and 126b which perform correction so that the laser beam subjected to isometric speed deviation by the polygon mirror 123 is subjected to isometric speed deviation on the photosensitive member 101, and a mirror 127. The laser beam detecting means 118 comprises a BD mirror 128, BD convergence lens 129, and BD substrate 130, in which a portion of the laser beam is reflected by the BD mirror 128, converged by the BD convergence lens 129, and detected by the BD substrate 130. The existence of the laser beam can be detected from the signals obtained by the BD substrate 130, and this is generally used for knowing detection of the laser starting timing.
With reference to FIG. 13 once more, the electrophotography processing unit 115 follows the form of a known electrophotography method, and comprises a charging unit 131, developing unit 132, transferring unit 133, and charge eliminating unit 134, provided in the proximity of the photosensitive member 101 and in this order in the direction of rotation of the photosensitive member 101, and further comprises a fixing unit 135.
The paper feeding unit 104 is for feeding the paper loaded in the cassette 136 from the very top thereof out to the conveying path 137 so as to be conveyed toward the laser printer unit 103 following the conveying path 137, and comprises a paper feeding roller 138 and conveying roller 139 for conveying paper.
Also, provided downstream in the paper-conveying direction from the fixing unit 135 is a conveying path 140 leading to a sorter 105 and a conveying path 141 leading to the paper feeding unit 104, these being switched between by a reversal gate. The later conveying path 141 branches into a reversal conveying path 142 which is used in the case where both-side copying is performed with the paper feeding unit 104, and a both-side/synthesizing conveying path 143 used for both-side copying and synthesizing copying. Further, the conveying path 137 of the paper feeding unit 104 merges with the both-side/synthesizing conveying path 143 and conveying path from the manual-feed original tray 113 and leads to an image forming position between the photosensitive member 101 and the transferring unit 133.
Accordingly, the image data read from the data reading unit is output from the laser scanning means 117 as a laser beam, and forms an electrostatic latent image on the surface of the photosensitive member 101. This electrostatic latent image is visualized by toner of the developing unit 132, and following this toner image being transferred onto the paper conveyed from the paper feeding unit 104, the toner image is fixed upon the paper by the fixing unit 135. This paper is sent from the fixing unit 135 to the sorter 105 via the convey path 140, or is conveyed to the paper feeding unit 104 via the conveying path 141 where both-side or synthesized copying is performed.
Now, as shown in FIG. 15, this clamshell-type digital photocopier is of a frame structure, comprised of a lower first main unit 150 which is stationary, and an upper second main unit 151 which opens and closes as to the first main unit 150.
Provided to the first main unit 150 are the paper feeding unit 104, sorter 105, and the transferring unit 133, charge eliminating unit 134, and fixing unit 135 of the electrophotography processing unit 115. In the second main unit are provided the scanner unit 2, and the laser printer unit 103 excluding the transferring unit 133, charge eliminating unit 134, and fixing unit 135. The first main unit 150 and second main unit 151 are linked by a fulcrum 152, so that the second main unit 151 is rotatably supported so as to open vertically, the open state being maintained by a damper.
In the side opposite the fulcrum 152 is provided a locking mechanism comprised of a locking piece 153 on the first main unit side and a locking lever 154 on the side of the second main unit side for detachably engaging the locking piece 153, for locking the second main unit 151 to the first main unit 150 when closing the second main unit 151.
With known digital photocopiers, the laser recording unit 114 has been fixed to the second main unit 151 by screws or the like. Accordingly, in the case where the photocopier is moved, or in the case where the photocopier receives external shock or vibrations, the laser recording unit 114 receives the shock or vibrations in full. Also, in the case of opening and closing the second main unit 151 for dealing with trouble such as paper jamming or the like, the laser recording unit 114 receives the shock or vibrations in full.
In the case that the laser recording unit 114 receives shock or vibrations in full in this way, the semiconductor laser, f-.theta. lenses 126a and 126b, mirrors 123 and 127, and so forth, which comprise the laser recording unit 114, may shift in position, which can cause undesirable effects on the image quality, such as the laser beam irradiation position shifting. Particularly, in the event that such shock or vibrations are applied during inertial rotation of the polygon motor 125 which is a component of the laser recording unit 114 following termination of driving thereof, this can lead to damage to the motor shaft which rotates at high speeds, the bearings, and other members which also are vulnerable to shock or vibration.
Regarding the vertically divided type laser recording apparatus, examples of art for preventing shock and vibrations from effecting the laser recording unit 114 are disclosed in Japanese Examined Patent Publication JP-B2 63-56984 (1988), Japanese Unexamined Patent Publication JP-A 61-28967 (1986), and Japanese Unexamined Patent Publication JP-A 1-189665 (1989).
In order to reduce the shock and vibrations to prevent damages to the bearings and the like of the laser scanning means, the laser recording apparatus disclosed in Japanese Examined Patent Publication JP-B2 63-56984 (1988) is arranged such that disengagement of the locking mechanism is forbidden during recording operation, and in the case where a certain amount of time has passed following termination of supply of driving force to the laser scanning means or where detection has been made that the laser scanning means has either stopped or the rotation thereof has decreased to a certain speed or slower, the disengagement of the locking mechanism is permitted and opening of the main unit is enabled. However, with the above apparatus time is spent before opening the main unit in order to remove jammed paper or the like, which is disadvantageous for effective maintenance. Also, since a mechanism equivalent to the laser recording unit is integrally opened with the processing means comprising the electrophotography processing unit, maintenance work of cleaning and adjusting the mechanism equivalent to the laser recording unit is difficult.
In order to avoid change in scanning line pitch and main scanning speed owing to the vibration and shock, the laser recording apparatus disclosed in Japanese Unexamined Patent Publication JP-A 61-28967 (1986) is arranged such that scanning means including a rotational polygon mirror are provided on the side of the vertically divided casing to which a shaft providing as a fulcrum thereof is provided. In this arrangement as well, a mechanism equivalent to the laser recording unit 114 is integrally opened with a mechanism equivalent to the electrophotography processing unit 115, so maintenance work of the mechanism equivalent to the laser recording unit is difficult.
Further, in order to prevent deterioration of optical precision owing to the vibration and shock, the electrophotography apparatus disclosed in Japanese Unexamined Patent Publication JP-A 1-189665 (1989) is arranged such that an optical system unit is divided into a light scanning unit which scans an optical beam from a light source and a reflecting mirror which irradiates the optical beam from the light scanning unit onto a photosensitive member, and the light scanning unit, photosensitive member, and peripheral members thereof are placed in the stationary lower case, while the upper case openably attached to the lower case being provided with the reflecting mirror. According to this electrophotography apparatus, the photosensitive member and the peripheral members are provided in the lower case, so little space is exposed even with the upper case opened. Thus, removing paper jammed in the convey path, for example, is difficult.